Another helpful item might be a headlamp. I saw a couple in West Marine the other day that were LED's. They are super bright. I think we all know the drill where we are trying to fix something in a dark space and there is no place to put the flashlight where it is going to shine in just the right place.

The largest slip joint pliers you can get. You know the really humongous ones that you'd never use, yeah right!! A pair of those has been invaluable for working on those really large nuts, like the packing gland, that you probably don't have a sized wrench or Crescent to fit. Truly an emergency tools.